The overall goal of this research proposal is to identify and characterize the gene which causes the common human genetic disease, primary hemochromatosis (PH). PH is an autosomal recessive disease that causes heart and liver failure due to iron overload. It is the most common genetic disease of the liver with a prevalence of 3-8/1,000, in the North American population. Unfortunately, pre-symptomatic diagnosis of PH is difficult; and it is often mis-diagnosed. Good, inexpensive, and accessible preventative treatment is available if the diagnosis can be made before irreversible organ damage occurs. Identifying the gene will permit pre-symptomatic diagnoses. Since the biochemical alteration that leads to PH remains unknown, a positional cloning strategy is proposed for finding the PH gene. The broad location of the gene within the HLA region on chromosome 6p2l.3 was discovered by its' linkage to the HLA serological marker, HLA-A3. The specific aims of this strategy are to construct physical and genetic maps of the relevant chromosomal region and in particular to carefully define the boundaries of the PH locus; To then select out all the genes encoded within the PH locus and characterize them in terms of sequence homologies and motifs, and patterns of expression; To functionally assay the selected genes for their potential affects on cellular iron flux in-vivo; And finally to confirm PH gene candidates by mapping mutations through affected pedigrees.